Medical grasping device

ABSTRACT

A medical grasping device ( 10 ) for vascular use, having an outer sheath ( 12 ), an elongate control member ( 50 ) extending within an outer sheath ( 12 ) to a distal tip section ( 54 ), and a proximal control assembly ( 22 ) including an actuation section ( 24 ) joined to the elongate control member ( 50 ). Adjacent to the distal tip section ( 54 ) is a grasping portion ( 70,70 ′) that is extendable from the outer sheath ( 12 ) to create loops ( 74,74 ′) for grasping a target object (T) for repositioning within the vascular system, or for removal from the patient, with loops being retractable into the outer sheath to hold the target object against the device ( 10 ) during movement of the device. Elongate control member ( 50 ) is preferably a cannula or tube having a lumen ( 58 ) extending completely therethrough for placement over a guide wire ( 28 ) already in the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part to U.S. patent applicationSer. No. 10/003,011, filed Nov. 1, 2001, which claims priority toProvisional Patent Application Ser. No. 60/245,811 filed Nov. 3, 2000.

TECHNICAL FIELD

This invention is related to medical devices and in particular to amedical grasping device.

BACKGROUND OF THE INVENTION

There is a current trend in medicine to minimize surgical andinterventional procedures, concomitant with the development of minimallyinvasive tools to access, visualize, infuse, treat, medicate, sample,and interact with internal structures of the body. Occasionally, devicessuch as catheters, balloons or wires are inadvertently severed in ablood vessel, cavity or organ. Depending on its location, the severeddevice or fragment must be retrieved. Frequently, a surgical approach isdangerous and costly. In many cases, access has already been establishedto the severed device, fragment, or foreign body in question, and it isjust a matter of locating and removing the foreign body without doingharm to surrounding tissue or forcing it further out of reach.

Certain medical devices are known that are utilized in the ducts andvessels of a human or veterinary patient for retrieval of bodies fromthe patient. For example, retrieval devices are known for removingcalculi such as kidney stones or gallstones from a patient, where theretrieval device is delivered to the target site via the urethra orbiliary duct, respectively. The device=s distal tip is adapted to deployat the site to form a basket shape to trap the calculi after which thebasket is collapsed to grasp the calculi. Both the device and thegrasped calculi are then withdrawn from the patient.

One such stone retrieval device is disclosed in U.S. Pat. No. 5,989,266,in which several loops of wire are caused to emerge from the distal endof a sheath that has previously been delivered through the renal orbiliary system of a patient to the site of the stone. The stone becomestrapped within the loops, after which the loops are pulled proximallymostly into the sheath, grasping the stone firmly, after which thesheath, loops and stone are withdrawn from the patient. The loops aredisclosed to be made from a superelastic alloy such as nitinol toautomatically form the loops when caused to emerge from the sheath=sdistal tip. Other similar stone retrieval devices are disclosed in U.S.Pat. Nos. 5,057,114; 5,064,428; 5,133,733 and 5,484,384.

However, use of such devices is not satisfactory for grasping such anobject within the vascular system of a patient for repositioning of thatobject, or for removal of objects from within the vascular system of apatient. For example, in certain situations it is desired to repositiona stent or stent graft within the vasculature, or to retrieve orreposition a malpositioned or misplaced embolization coil. And duringdelivery and deployment of a bifurcated stent graft at the site of anabdominal aortic aneurysm when surgical access has been obtained throughthe femoral arteries on both sides of the groin, it is desirable tograsp the distal tip of a guide wire extending into the aneurysm fromthe contralateral iliac artery, to be pulled into the ipsilateral iliacartery at the vessel=s aorto-iliac bifurcation, for eventual placementof the contralateral leg extension of the stent graft.

For vascular use, another known device is a suture loop on a catheterdistal tip. Yet another is a guide wire that has been doubled over andextended through a catheter so that its distal end forms into a loopthat extends axially from the catheter=s distal end to be utilized as aretriever when it is pulled proximally to capture an object and hold itagainst the catheter distal end for withdrawal, sold as the CurryIntravascular Retriever Set by Cook, Incorporated, Bloomington, Ind. Aversion of the stone basket device, having helical loops, has beenutilized for intravascular retrieval, the Dotter Intravascular RetrieverSet also sold by Cook, Incorporated.

In U.S. Pat. No. 5,171,233 is disclosed a snare-type probe forintravascular use. After a catheter is inserted into the patient=svascular system to the site of the foreign object, an elongate memberhaving a loop-shaped distal segment is inserted into the proximal end ofthe catheter=s lumen until the loop-shaped distal segment emerges fromthe catheter=s distal tip at the site. Then the loop-shaped segmentextends at an angle to the adjacent portion of the member and opens intoa loop. Once a free end of the foreign object is snared within theloop-shaped distal segment as determined by fluoroscopic equipment, theloop-shaped distal segment is pulled proximally into the catheter distalend, collapsing about the ensnared foreign body fragment and holding theforeign body at the distal tip of the catheter during withdrawal. Theelongate member is preferably disposed within an outer sheath and isdisclosed to be one wire, or two gripped-together wires, of a shapememory material such as a superelastic nitinol alloy, with a singlepreformed loop shape at the distal segment defined by two wire portions.The use of nitinol enables the wire segments defining the distal segmentto be straightened and collapsed upon one another into an elasticallydeformed configuration to pass through the lumen of the catheter and yetautomatically open into a loop and extend at a substantial angle uponemerging from the catheter distal tip. One characteristic of this designis that during retraction after grasping, the loop quickly changes, orAflips,@ between the angled orientation and a generally axial one, andthis results in less assured control over the item during grasping, andcommonly will result in escape of the item thus requiring redeploymentof the loop for another grasping attempt.

It is desired to provide a medical grasping device for grasping andrepositioning an object within the vascular system of a patient, such asa stent or stent graft or embolization coil or such as the distal tip ofa catheter or a guide wire; or to grasp a stent or embolization coil, ora fragment from a catheter or guide wire or a pacemaker lead, for itsremoval from the patient.

It is also desired to provide a low profile, medical grasping devicethat is conformable to the vascular anatomy while generating asubstantial tensile force.

It is further desired to provide such a device that is trackable throughthe vascular system over a guide wire already in situ.

It is yet further desired to provide such a device that is atraumatic tothe patient.

It is still further desired to provided a grasping device having atension absorbing feature to absorb tension at the elongate memberduring retraction, thereby lessening the likelihood of disengagement ofthe elongate member from the device.

BRIEF SUMMARY OF THE INVENTION

The foregoing problems are solved and a technical advance is achieved inan illustrative embodiment of a medical grasping device of the presentinvention. The grasping device includes an outer sheath and an elongatecontrol member that is relatively axially movable with respect theretowithin a passageway of the outer sheath when actuated by a proximalcontrol assembly. The elongate control member is formed for lowelongation. In a first aspect of the present invention, when in theretracted state, an atraumatic distal tip section of the elongatecontrol member extends forwardly beyond the distal end of the outersheath, especially of value during placement of the grasping devicewithin the vascular system of a patient to reach the target site of theobject to be grasped. Just proximal of the atraumatic distal tip sectionis the grasping portion of the device, restrained within the distal endportion of the outer sheath until actuated.

In a second aspect, preferably, the grasping portion defines a pluralityof preformed wire loops that smoothly deploy laterally when the elongatecontrol member is moved distally urging the wires to emerge from thedistal end of the outer sheath, and that smoothly resume an axialorientation when being retracted into the outer sheath while the loopsare being reduced in size, thus assuredly snaring the object.

In a third aspect of the invention, the wire loops are formed from asuperelastic alloy such as nitinol, so that the loops are easilycollapsible for insertion into the outer sheath and movement therealongduring assembly, and for actuation and later retraction into the outersheath distal end after grasping, and so that the loops automaticallyform upon actuation of the device and emerging from the outer sheathdistal end to traverse the cross-section of the vessel. The wiresegments are affixed to the distal portion of the elongate controlmember, where the elongate control member is preferably of a differentmaterial.

In a fourth aspect of the invention, the grasping portion comprises aplurality of loops, such as preferably four loops that define aclover-leaf shape, that extend at a substantial angle to the axis of thecannula, and preferably transverse thereto upon full deployment so thatthe four loops together generally occupy the full cross-section of thevessel. As the loops are emerging from the sheath distal end, the wiresegments initially are axially oriented but begin to deflect radiallyand diverge from one another as the loops begin to open. Preferably,even when the loops are fully formed and transversely oriented, thesegments of the wires forming the loops extend in a continuous fashionto axially aligned end portions at the affixation joints with theelongate control member. Where the vessel diameter is less than thegeneral outer envelope formed by the four loops if deployed when fullyunrestrained, the loops will generally fill the vessel until engagementwith the vessel walls inhibits full transverse orientation whereupon theloops are angled and opened.

In a fifth aspect of the invention, the elongate control member ispreferably a flexible cannula or tube defining a lumen extendingtherethrough for a guide wire to be received thereinto, for placementonto and passage of the device over a guide wire so that the graspingdevice is easily and quickly guided to the treatment site by a guidewire already in place in the patient. The lumen extends through thegrasping portion and the atraumatic distal tip section so that thedevice is insertable over the exposed proximal end of the guide wirethat is already in situ. Such an over-the-wire advantage: allows accessto tortuous anatomy and multiple side branches; obviates the need toremove the guide wire to permit insertion of the grasping device intothe patient; obviates the otherwise tedious procedure of guiding(without the benefit of guidance and support of a guide wire) the outersheath device through the vasculature of the patient to the target site;and obviates the need to later reinsert the previously-removed guidewire following eventual removal of the grasping device, for possibleadditional treatment procedures of various kinds; and all therebyresults in much-reduced treatment time and much-reduced risk to thepatient.

In a sixth aspect of the invention, the grasping device preferablyincludes hemostatic sealing between the outer sheath and the elongatecontrol member.

In additional aspects, the grasping device includes a proximal controlassembly that is easily manipulated for actuation during grasping, andfor assured continued automatic grasping of the object with acontrolled, limited amount of force while the device is being moved tomanually reposition the object or to remove it completely. The elongatecontrol member is formed to have torqueability and significant tensilestrength with high elongation at its proximal end portion and a lowelongation distal to the proximal end portion. The outer sheath has aflexible but kink-resistant construction with lubricious outer and innersurfaces.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be disclosed by way ofexample with reference to the accompanying drawings, in which:

FIG. 1 is an elevation view of the grasping device of the presentinvention;

FIG. 2 is an enlarged partial section view of the device of FIG. 1;

FIG. 3 is an exploded elevation view showing the components of thegrasping device of FIGS. 1 and 2;

FIG. 4 is an enlarged view of the grasping portion of the device;

FIG. 5 is an isometric view illustrating one of the wire segmentsdefining one of the loops;

FIGS. 6 to 9 are enlarged cross-sectional views of the grasping portionand distal tip of the device prior to deployment, during deployment,fully deployed, and partially retracted after grasping a target catheterend, respectively;

FIG. 10 is an enlarged end view of the distal end portion of the deviceillustrating the grasping portion of the device fully deployed;

FIG. 11 is an enlarged end view of an alternate embodiment of thegrasping portion of the present invention; and

FIG. 12 is an enlarged view of the actuation section of the proximalcontrols.

DETAILED DESCRIPTION OF THE INVENTION

With regard to FIGS. 1 to 3, grasping device 10 of the present inventionincludes an outer sheath 12 extending from a distal end portion 14 to aproximal end 16. Secured to the proximal end 16 is proximal controlassembly 22 including a handle 20 that is affixed to the outer sheath12. Proximal control assembly 22 also includes an actuation section 24that is movably affixed to the handle 20, and that is in operativerelationship with an elongate control member 50 that is disposed withinouter sheath 12 and extends along passageway 18 completely therethroughto a distal end portion 52 that is adjacent to distal end portion 14 ofouter sheath 12. Outer sheath 12 also includes adjacent to its distalend 30 a radiopaque marker band 32. Distal end portion 52 of controlmember 50 concludes in a distal tip section 54, and spaced proximallyfrom the proximal end 56 of distal tip section 54 is the graspingportion 70 of the present invention.

Elongate control member 50 is preferably a cannula or tube having aguide wire lumen 58 extending completely therethrough, for receipttherethrough of a guide wire 28. Guide wire 28 need not be part of thegrasping device 10 of the present invention, but the present inventionis particularly designed to be used therewith and would be of the typeconventionally in use for various intravascular procedures. Elongatecontrol member 50 has an outer diameter that is less than the innerdiameter of passageway 18 to enable relative axial movement within theouter sheath 12 when actuated. Elongate control member 50 has a distaltip section 54 that is blunt and rounded to be atraumatic to thepatient, preferably tapered to its rounded tip from the outer surface ofouter sheath 12 at distal sheath end 30 to provide a smooth transitionbetween the outer sheath and the guide wire 28. The atraumatic tipprotects the vessel wall and reduces the chance that the distal tip ofthe grasper device will shear off any atheromatous plaque that itencounters while tracking through the vascular vessel. At proximal endportion 60 of elongate control member 50 is a connection 62 to actuationsection 24.

A side flushport fitting 96 with a T-shaped lumen therein is affixed tothe front end of handle 20 such as by snap coupling 98 and securestherewithin a seal 36 surrounding control member 50, such as a flatflexible sealing washer, and holds it tightly against the front end ofhandle 20. Seal 36 defines hemostatic sealing of passageway 18 aroundcontrol member 50. A cap 38 attaches outer sheath 12 to a threadedforward portion of adapter fitting 34. Cap 48 keeps the lumen offlushport fitting 96 sealed when not connected to a fluid source.Preferably, outer sheath 12 includes an enlarged or flared proximal end40 on proximal end 16 that is tightly gripped by cap 38, and enlargedproximal end 40 may be complementary to a conical forward end ofthreaded forward portion of fitting 34. Handle 20 preferably includes athumb ring 42. Seen extending rearwardly and at a gradual anglelaterally from handle 20 is tubing 44 that is affixed to the rearwardend of control member 50 and having a passageway along which guide wire28 extends, with tubing 44 including thereon a Touhy-Borst adaptor 46,for hemostatic sealing around the guide wire proximally of controlmember 50.

Referring now to FIGS. 4 and 5, the grasping portion 70 is preferablydefined by wire segments 72 that define loops 74. Wire segments 72 arepreferably fabricated from a superelastic material such as nitinol.Proximal ends 76 of the wire segments may be affixed to the controlmember at affixation joints 78, such as by low-temperature soldering asin U.S. Pat. No. 5,354,623, or, less preferably, welding to a stainlesssteel band 80 that is affixed to distal end portion 52 of control member50 such as by crimping or bonding.

As depicted in FIG. 8, each loop 74 of grasping portion 70 includesarcuate outer sections 82 that extend to be adjacent or in abutment withwall 84 of vessel 86. Each loop 74 also includes arcuate side sections88 that extend toward the axial center of the grasping portion 70 andthen curve gradually toward the distal end of the control member andaffixation joints 78. Preferably, wire segment proximal ends 76 coextendcoaxially at least distally along the outer surface of the controlmember 50 from the affixation joints 78, and continuously and graduallyextend to those portions that will define loops 74 upon emerging fromouter sheath 12 upon actuation. Also, preferably, proximal ends 76 thatare affixed to the control member are within the cold-worked bend 74A ofthe nitinol wire segment (FIG. 5), since this assures the gradualcurving of that portion of loop 74 adjacent the axis as it emerges fromthe distal end of the outer sheath. As depicted in FIG. 5, fabricationof the affixation joints may be most easily accomplished if the wiresegment 72 initially includes unbent straight segments 76A extendingfrom ends 78A of loop 74A for ease in controlled forming, handling andpositioning of the wire segment, after which at least most of segments76A are removed.

Soldering of nitinol to stainless steel is disclosed in U.S. Pat. No.5,354,623. Wire segment proximal ends 76 may also be secured by bondingor another form of affixation directly to control member 50 or toanother intermediate member similar to band 80. Forming of the wireloops from nitinol may be attained by stress-inducing the wires intothat shape during heat treatment or annealing of the grasping portion inthe loop shape to create stress-induced martensite (SIM) at the loops asdisclosed in U.S. Pat. No. 5,597,378 while the remainder of the wireshas an austenitic state. The preforming of the loops may also beattained by cold-working the loops as is disclosed in PCT Publication WO00/33909, by over-bending a wire in the austenitic state about afixture. Cold-working permanently locks a portion of the crystallinestructure of the bending zone into at least a partial martensiticcondition while the unstressed portions of the wire remain in theaustenitic state.

Referring now to FIGS. 6 to 9, grasping portion 70 is shown in moreparticularity. In FIG. 6, grasping portion 70 is seen in its recessedstate within distal end portion 14 of outer sheath 12, as atraumatic tipsection 54 extends beyond distal sheath end 30 from control member 50.Wire segments 72 are held entirely within outer sheath 12, along distalend portion 52 of control member 50 distally of affixation joints 78 andextending axially from proximal wire portions 76. Affixation joints 78are disposed preferably within stainless steel band 80. Loops of thewire segments 72 are seen in a constrained condition 74B along thecontrol member just proximally of proximal end 56 of atraumatic distaltip section 54. Outer sheath 12 preferably includes a radiopaque markerband 32 around its outer surface at distal end portion 14 a smalldistance from sheath end 30.

FIG. 7 illustrates partial deployment of grasping portion 70. It isclearly seen that wire segments 72 curve gradually and continuously fromcontrol member 50 forwardly and eventually radially outwardly to outersections 82 beyond sheath end 30 during deployment as the loops 74 beginto open, and exhibit a corollary curving during retraction into outersheath 12.

In FIG. 8 is seen grasping portion 70 fully deployed within vessel 86,with outer sections 82 of loops 74 abutting vessel wall 84. Guide wire28 is seen extending forwardly from atraumatic distal tip section 54.Proximal wire segment sections 76 are seen to maintain a continuous,gradual curvature as they exit from distal end 30 of outer sheath 12 toform loops 74.

A target object T has been snared by grasping portion 70 in FIG. 9, andgrasping portion 70 has been mostly retracted into outer sheath 12 sothat the target object is held firmly against outer sheath 12, andnearby portions of atraumatic distal tip section 54 and possibly distalend portion 52 of control member 50 adjacent to tip section 54. In thisinstance, the target object is a catheter whose end portion is to berepositioned.

Loops 74 are shown in FIG. 10 as substantially circular, extending toarcuate outer sections 82 with arcuate side sections 88 that extendtoward the center of the grasping portion 70 and then curve toward thedistal end of the control member and affixation joints 78. Side sections88 of each loop 74 are seen to overlap to some extent with side sections88 of adjacent loops 74. Altogether, when arcuate outer sections 82 abutthe vessel wall 84 of vessel 86, the loops 74 are seen to traversesubstantially the entire cross-section of the vessel.

In FIG. 11 is shown an alternate embodiment of grasping portion 70′.Grasping portion 70′ comprises four pie-shaped loops 74′, each definedby wire segments 72′ that preferably are superelastic material such asnitinol. Each pie-shaped loop 74′ includes an outer section 82′ that isarcuate for abutment against the vessel wall 84 of vessel 86 and havinga radius about equal to the radius of the vessel at the target site, andopposed radial side sections 88′ converging to the center of thegrasping portion. It can be seen the entire cross-section of the vessel86 is traversed by the grasping portion when deployed. As with graspingportion 70 of FIG. 10, side sections 88′ may overlap those of adjacentloops 74′.

With reference now to FIGS. 2, 3 and 12, proximal control assembly 22 isshown in greater particularity and includes an ergonomic easilygrippable spool-shaped slide member 100 that is reciprocally movablealong handle 20 to in turn actuate control member 50 to move withrespect to outer sheath 12 attached to handle 20. Slide member 100 isfastened such as by set screws 102 to a connecting block 104 that isaffixed to control member 50 extending into a central passageway 106 ofhandle 20 through cap 38, fitting 34 and flushport 96. Connecting block104 is shown to be disposed within a slot 108 of handle 20. Slot 108thus defines the limits of movement of connecting block 104 and thus ofcontrol member 50. Connecting block 104 includes an axial openingtherethrough and is affixed to the proximal end of control member 50such as by being disposed rearwardly of an annular forward stop collar110, after which a barbed fitting 112 is placed onto the projectingrearward end 114 of control member 50 rearwardly of the connecting block104 to form the rearward stop.

FIG. 12 illustrates the proximal end portion 60 of the elongate controlmember 50 being comprised of a different material than the remainingportion of the elongate control member 50. In this embodiment, theproximal end portion 60 is comprised of a high elongation material 61proximally bonded to the elongate control member 50 which is comprisedof a low elongation material 63. The high elongation material allowselongation of the elongate control member 50 when the elongate controlmember 50 is moved distally urging the wires 72 to emerge from thedistal sheath end 30 of the outer sheath 12. The high elongationmaterial 61 at the proximal end portion 60 serves to absorb tension byelongation, lessening the likelihood of unwanted disengagement of theelongate control member 50 from the proximal control assembly 22. Thelow elongation material 63 minimizes elongation of the elongate controlmember 50 when the elongate control member is moved proximally urgingthe wires 72 toward the outer sheath 12 during removal of a targetobject.

As shown, the high elongation material 61 is preferably thermally bondedto the low elongation material 63 of the elongate control member 50distal from the annular forward stop collar 110. Of course, the highelongation material 61 may be bonded to the elongate control member 50at a location proximal to the annular forward stop collar withoutfalling beyond the scope or spirit of the present invention. The highelongation material 61 is preferably a thermoplastic material thermallybonded to the elongate control member 50. The high elongate material 61may be comprised of a softer and lower durometer material, e.g., a lowdensity polymer, than the low elongate material 63. It is understoodthat the high elongate material 61 and low elongate material 63 arecompatible materials so that each can be thermally bonded to the otherwithout substantially compromising the characteristics of either.Additionally, it is understood that any suitable high elongationmaterial may be used.

Barbed fitting 112 also sealingly secures tubing 44 to rearward end 114of control member 50. Preferably, the rearward end of slot 108 isscalloped to define a controlled shallow exit for tubing 44, throughwhich will extend guide wire 28.

Actuation section 24 may preferably include a spring-loaded retractionsection (not shown) that upon manual release thereof retracts thegrasping portion 70,70′ into the distal end portion 14 of the outersheath 12, and simultaneously captures the target body T within one ofthe loops 74,74′ so that it is held against distal sheath end 30 anddistal end portion 52 of control member 50 (see FIG. 9).

The retraction section may further include a lock (not shown) thatenables the grasping portion to automatically hold the grasped object Twith a preselected limited grasping force during movement of thegrasping device by the practitioner; such lock may be of the ratchetkind that may be manually set by the practitioner after sufficientgrasping has been attained for the immediate purpose. The limited amountof force thus would protect the grasped object from damage especiallywere it to be of continued value in treating the patient afterrepositioning thereof.

Outer sheath 12 is very similar to a guiding catheter in structure andfunction, and may be formed for example with an inner liner ofpolytetrafluoroethylene and an outer jacket of a polyamide such asnylon, and may be reinforced such as by a spiral-wound flat stainlesssteel wire coil embedded between an inner nylon liner and an outerjacket, all in a manner disclosed in greater detail in U.S. Pat. No.5,769,830 in order to be kink-resistant. The outer surface of the outerjacket may be coated for example with a lubricious material such as AQTMHydrophilic Coating. The control member 50 may be formed for example ofthermoplastic material such as polyethylene terephthalate. The distaltip section 54 may be a separate member of a softer, lower durometermaterial of conventional composition. Lumen 58 preferably has a diameterof up to 0.040 in to allow free passage over guide wires that would havediameters of up to 0.038 in as is common.

Elongate control member 50 may be fabricated by braiding of the materialdistal to the high elongation material at the proximal end portion 60 ina manner that imparts the ability of the control member to be torqued,that is, to be rotated by the proximal control assembly 22 for adjustingthe grasping portion about the axis, if desired. Such braiding should befrom such materials and in such a manner that does not result innoticeable elongation of the control member 50 distal from the highelongation material of the proximal end portion 60 during retraction ofthe grasping portion, or withdrawal of the device during total removalof the target object.

The device includes a flushport fitting to allow flushing with sterilesaline solution between the elongate control member and the outer sheathto eliminate air, while the device is outside of the patient. An airseal can be utilized near the distal end of the sheath.

The grasping device of the present invention can be useful in anymultiple access vascular procedure for adjusting the final position of amedical device, such as through the iliac or subclavian arteries. Theinvention can additionally be useful with the liver or kidney or othernonvascular procedure, especially where access to the site involves atortuous path, since the grasping device is flexible and is adapted tofollow a guide wire.

1. A medical grasping device comprising: an elongate control member having an atraumatic distal tip section and a proximal end portion, said elongate control member further including a grasping portion proximal said distal tip section, said elongate control member being formed for low elongation; an outer sheath with a passageway therethrough surrounding said elongate control member and relatively movable with respect thereto; and a control assembly disposed at a proximal end of said outer sheath and said proximal end portion of said elongate control member and in operative relation thereto for urging said grasping portion from a distal end of said outer sheath and retraction thereinto.
 2. The grasping device of claim 1, wherein said elongate control member is a flexible cannula defining a lumen extending therethrough into which a guide wire is receivable and movable with respect thereto.
 3. The grasping device of claim 1 wherein the elongate control member is comprised of a low elongation material for low elongation distal to the proximal end portion and the proximal end portion is comprised of a high elongation material for tension absorption when the elongate control member is urged distally, the high elongation material being bonded to the low elongation material.
 4. The grasping device of claim 1, wherein said outer sheath is flexible and kink-resistant and has lubricious outer and inner surfaces.
 5. The grasping device of claim 1, wherein said atraumatic distal tip section tapers to a blunt and rounded tip.
 6. The grasping device of claim 1, wherein said control assembly includes an actuation section that is easily grippable for reciprocal movement along a handle to actuate said elongate control member with respect to said outer sheath to deploy and retract said grasping portion, respectively.
 7. The grasping device of claim 6, wherein said actuation section includes a connecting block affixed to said elongate control member and is disposed within a longitudinal slot of said handle and is movable along said slot between opposite ends thereof.
 8. The grasping device of claim 1, wherein said grasping portion comprises a plurality of preformed wire loops.
 9. The grasping device of claim 8, wherein said plurality of wire loops self-deploy transversely upon emerging from said distal end of said outer sheath.
 10. The grasping device of claim 8, wherein each of said wire loops is substantially circular upon full deployment.
 11. The grasping device of claim 10, wherein each of said wire loops includes side sections that overlap with side sections of adjacent ones of said wire loops.
 12. The grasping device of claim 8, wherein each of said wire loops is pie-shaped and includes arcuate outer sections having a radius about equal to a radius of a deployment site of a vessel into which the grasping device is inserted.
 13. The grasping device of claim 1, wherein said grasping portion comprises four preformed wire loops that self-deploy transversely upon emerging from said distal end of said outer sheath approximately equally spaced angularly about a longitudinal axis of said elongate control member and thereby generally occupy a full cross-section of a vessel into which the grasping device is inserted.
 14. The grasping device of claim 1, wherein said grasping portion comprises a plurality of wire loops that each are formed from a superelastic alloy.
 15. The grasping device of claim 1, wherein said grasping portion comprises a plurality of wire loops having proximal end portions that are joined to said elongate control member at affixation joints and initially extend axially from said elongate control member even when said wire loops emerge from said distal end of said outer sheath and self-deploy transversely of a longitudinal axis of the grasping device.
 16. The grasping device of claim 15, wherein each of said wire loops includes an arcuate outer section that upon deployment extends toward a wall of a vessel into which the grasping device is inserted.
 17. The grasping device of claim 16, wherein each of said wire loops includes arcuate side sections that extend toward an axial center of said grasping portion and then curve gradually toward said distal end of said elongate control member to proximal ends that are affixed by said affixation joints thereto and are in axial alignment therewith adjacent to said affixation joints.
 18. The grasping device of claim 17, wherein said wire loops comprise nitinol wire segments.
 19. The grasping device of claim 18, wherein each of said wire loops including said proximal ends are within a cold-worked bend of a respective one of said nitinol wire segments.
 20. The grasping device of claim 1, wherein: said elongate control member is a flexible cannula defining a lumen extending therethrough into which a guide wire is receivable and movable with respect thereto; said outer sheath is flexible and kink-resistant and has lubricious outer and inner surfaces; said control assembly includes an easily grippable actuation section along a handle to actuate said elongate control member with respect to said outer sheath; and said grasping portion comprises a plurality of preformed wire loops of nitinol that upon deployment extend generally forwardly and radially outwardly to substantially traverse the cross-sectional area of the vessel wall into which the grasping device is inserted, each of said wire loops including an arcuate outer section of complementary shape to a vessel wall portion upon deployment, and including side sections that extend toward an axial center of said grasping portion and then curve gradually toward said distal end of said elongate control member to proximal end sections that are affixed by affixation joints to said elongate control member and are in axial alignment therewith adjacent to said affixation joints.
 1. 21. A medical grasping device comprising: an elongate control member having an atraumatic distal tip section and a proximal end portion, the elongate control member further including a grasping portion proximal the distal tip section, the elongate control member being comprised of a low elongation material for low elongation distal to the proximal end portion, the proximal end portion being being comprised of a high elongation material for tension absorption when the elongate control member is urged distally; an outer sheath with a passageway therethrough surrounding the elongate control member and relatively movable with respect thereto; and a control assembly disposed at a proximal end of the outer sheath and the proximal end portion of the elongate control member and in operative relation thereto for urging the grasping portion from a distal end of the outer sheath and retraction thereinto. 